Field
The present invention relates to a driving circuit and a lighting apparatus for a light emitting diode, and more particularly, to a driving circuit and a lighting apparatus for a light emitting diode capable of improving a flicker, light efficiency, and electrical characteristics.
Discussion of the Background
Generally, a diode device for light emission such as a light emitting diode (LED) may be driven only by direct current (DC) power due to diode characteristics. Therefore, a light emitting apparatus using the existing light emitting diode has been restrictively used and should include separate circuits such as a switching mode power supply (SMPS) in order to be driven by alternating current (AC) power of 220V that is currently being used at home. Therefore, there is a problem in that a circuit of the light emitting apparatus is becoming more complicated and manufacturing costs thereof are rising.
In order to solve these problems, research into an LED that may be driven even by AC power by connecting a plurality of light emitting cells to each other in series or in parallel has been actively conducted.
In order to solve the problems in the related art as described above, a sequential driving scheme of LEDs using the AC power has been suggested. According to the sequential riving scheme, if it is assumed that a lighting apparatus includes three light emitting diode groups, under the situation that an input voltage is increased over time, a first light emitting diode group first starts to emit light at a first forward voltage level and a second forward voltage level higher than the first forward voltage level, a second light emitting diode group connected to the first light emitting diode group in series starts to emit light at the second forward voltage level and a third forward voltage level which is a voltage higher than the second forward voltage level, and the third light emitting diode group connected to the second light emitting diode group and the first light emitting diode group in series starts to emit light at the third forward voltage level and a fourth forward voltage level which is a voltage higher than the third forward voltage level. Meanwhile, under the situation that the input voltage is reduced over time, the third light emitting diode group first stops emitting light at the second forward voltage level and the third forward voltage level, the second light emitting diode group stops emitting light at the first forward voltage level and the second forward voltage level, and the first light emitting diode group finally stops emitting light at a voltage level which is equal to or less than the first forward voltage level, such that a driving current for the light emitting diode is designed to approximate to the input voltage.
However, the driving circuit for a light emitting diode based on the general sequential driving scheme may brings about the flicker at timing when each of the light emitting diode groups is sequentially driven. In particular, the driving circuit for the light emitting diode based on the general sequential driving scheme may bring about a flicker in a section where it is progressed from a high forward voltage level to a low forward voltage level.